Silicon carbide cladding slab based laser cooling device

ABSTRACT

A silicon carbide cladding slab based laser cooling device is disclosed. The cooling device includes two silicon carbide slabs, two heat sinks and two fans. The first and the second silicon carbide slabs are respectively diffusion bonded to both sides of a Nd:YVO 4  active material of a laser; the first and the second heat sinks are disposed on outer sides of the first and the second silicon carbide slabs, respectively; the first fan is facing the first heat sink and the second fan is facing the second heat sink. The present invention facilitates the operation and miniaturization of a high-energy Nd:YVO 4  slab laser at room temperature and ensures a stable high-energy laser output of the slab laser, thus providing a solution for its commercialization.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of Chinese patent applicationnumber 201110060968.X, filed on Mar. 15, 2011, the entire contents ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a device used in the field of opticalinstrument and in particular, relates to a silicon carbide cladding slabbased laser cooling device.

BACKGROUND

Nowadays, liquid cooling is commonly used as a cooling method for laserdevices. Although liquid cooling is effective, it is complex andinconvenient for design and experiment. In design, paths of coolingliquid, airtightness and other aspects must be taken into account;during the experiment, such problems as requiring a bulky cooling liquidcirculating device and appropriately arranging the liquid pipelinesbring great inconvenience, and also increase the complexity ofexperiment system design and affect the stability of operations.

A liquid cooling method is disclosed in the publication by HamishOgilvy, Michael J. Withford, Peter Dekker and James A. Piper, entitled“efficient diode double-end-pumped Nd:YVO₄ laser operating at 1342 nm”,published as Optics Express 11, 2411 2003. However, this method isrelatively complex and inconvenient for design and experiment.

The disclosed device is directed to solve one or more problems set forthabove and other problems.

BRIEF SUMMARY OF THE DISCLOSURE

An objective of the present invention is to provide a laser coolingdevice to facilitate the operation and miniaturization of a high-energyNd:YVO₄ slab laser at room temperature and to ensure a stablehigh-energy laser output of the slab laser, so as to provide a solutionfor its commercialization.

The present invention is implemented by the following technicalsolutions. A device for cooling a laser having a Nd:YVO₄ activematerial, the device comprising a first and a second silicon carbideslab, a first and a second heat sink, as well as a first and a secondfan, wherein the first and the second silicon carbide slabs arediffusion bonded to both sides of the Nd:YVO₄ active material,respectively; the first and the second heat sinks are soldered on theouter sides of the first and the second silicon carbide slabs,respectively; the first fan is facing the first heat sink and the secondfan is facing the second heat sink.

The first silicon carbide slab, the first heat sink and the first fanare configured to be coaxial with the second silicon carbide slab, thesecond heat sink and the second fan, respectively.

The first and the second silicon carbide slabs both have a larger sizethan the Nd:YVO₄ active material to form silicon carbide claddings.

The first and the second heat sinks are copper blocks with micro-groovesformed on their outside surfaces, and their inner surfaces are closelyconnected with the first and the second silicon carbide slabsrespectively.

Laser diode pump beams are introduced into the Nd:YVO₄ active materialfrom its side faces, and the heat generated during the experiment israpidly transferred to the heat sinks through the silicon carbide slabshaving a high conductivity and is quickly dissipated from the wholesystem by the fans, thus achieving a highly efficient cooling. As theexperiment device is designed to be completely symmetrical, the systemonly generates a temperature gradient in a vertical directionperpendicular to the surfaces of the active material, and the heat israpidly dissipated from the system along the vertical direction, therebyminimizing the harm of thermal stress to the experiment device andforming a basis for stably and efficiently producing high-energy laserbeams.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of the structure of the laser coolingdevice according to the present invention;

FIG. 2 shows a schematic diagram of the structure of a laser.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of theinvention, which are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

As shown in FIG. 1, the laser cooling device according to one embodimentof the present invention includes: a first silicon carbide slab 2, asecond silicon carbide slab 3, a first heat sink 4, a second heat sink5, a first fan 6 and a second fan 7, wherein the first and the secondsilicon carbide slabs 2 and 3 are diffusion bonded to both surfaces of aNd:YVO₄ active material 1 of a laser, respectively; the first and thesecond heat sinks 4 and 5 are respectively disposed on the outer sidesof the first and the second silicon carbide slabs 2 and 3; the first fan6 is facing the first heat sink 4 and the second fan 7 is facing thesecond heat sink 5.

The first silicon carbide slab 2, the first heat sink 4 and the firstfan 6 are coaxial with the second silicon carbide slab 3, the secondheat sink 5 and the second fan 7, respectively.

The first and the second silicon carbide slabs 2 and 3 both have alarger size than the Nd:YVO₄ active material 1 to form silicon carbidecladdings.

The first and the second heat sinks 4 and 5 are copper blocks withmicro-grooves formed on their outside surfaces, and their inner surfacesare closely connected with the first and the second silicon carbideslabs respectively.

As shown in FIG. 1 and FIG. 2, the Nd:YVO₄ active material 1 is pumpedfrom its side faces by laser diodes 8. A resonant cavity is formed by areflecting mirror 9 and an output coupling mirror 10. By sandwiching theNd:YVO₄ active material 1 between the silicon carbide slabs 2 and 3which have a high thermal conductivity, the heat generated by the activematerial 1 during the laser producing process is rapidly transferred tothe heat sinks 4 and 5 disposed on both sides, and is further dissipatedfrom the experiment device by the fans 6 and 7 beside the heat sinks 4and 5. By utilizing symmetrically designed structures on both sides ofthe active material 1, the direction of temperature gradient in thematerial is corresponding to the normal line direction of both surfacesof the active material 1, and the heat is rapidly transferred along thisdirection by the silicon carbide slabs 2 and 3 to reduce the influencecaused by thermal stress to the system, thus achieving high-energy laseroutput at room temperature without using liquid cooling.

The present invention can achieve 100-watt-level laser output at roomtemperature by using special materials. The fact that the thermalconductivity of silicon carbide is very high while its thermal expansioncoefficiency is very close to that of Nd:YVO₄ provides a basis for thepresent invention. There are many deficiencies in diffusion bonding theNd:YVO4 active material to a conventional copper heat sink, for example,the active material is extremely easy to distort and even fracture underthermal stress when it is heated; besides, the copper will absorb a partof the pump beam and thereby reducing the absorption efficiency of thepump beam. The present invention adopts silicon carbide slabs, on theone hand, the Nd:YVO₄ active material can be closely diffusion bonded tothe silicon carbide slabs by way of diffusion bonding to effectivelytransfer the waste heat. Since these two materials have similar thermalexpansion coefficiencies, heat distortion of the active material iscoincide with that of the silicon carbide slabs when the active materialis heated, therefore, the fracture of the active material and thediffusion bonding layers can be effectively avoided. On the other hand,as silicon carbide material has an excellent optical property, the pumpbeam can transmit in the completely transparent silicon carbidematerial, thus resolving the issue of beam absorption existed inconventional copper heat sinks, and in this way, increasing theabsorption efficiency and laser output efficiency of the system.Moreover, as the outside surfaces of the silicon carbide slabs are incomplete contact with the copper heat sinks, waste heat is transferredto the copper heat sinks by the silicon carbide materials with highthermal conductivity, and further, as the copper heat sinks havemicro-grooves on outside surfaces, air flow provided by the fans cansufficiently contact with copper heat sinks and carry the waste heat offthe experiment device, so as to ensure a high-energy laser output.Compared with conventional liquid cooling experiment devices, thepresent invention can obtain a high-power laser output by using asimplified structure, which shows the advantages of novel air coolingdevices.

1. A cooling device for a laser having a Nd:YVO₄ active material, comprising: a first and a second silicon carbide slab, diffusion bonded to both sides of the Nd:YVO₄ active material respectively; a first and a second heat sink, respectively disposed on an outer side of the first and the second silicon carbide slabs; and a first and a second fan, respectively facing the first and the second heat sinks.
 2. The cooling device according to claim 1, wherein: the first silicon carbide slab, the first heat sink and the first fan are configured to be coaxial with the second silicon carbide slab, the second heat sink and the second fan, respectively.
 3. The cooling device according to claim 1, wherein: the first and the second silicon carbide slabs have a larger size than the Nd:YVO₄ active material to form silicon carbide claddings.
 4. The cooling device according to claim 1, wherein: the first and the second heat sinks are copper blocks with micro-grooves formed on outside surfaces, inner surfaces of the copper blocks being closely connected with the first and the second silicon carbide slabs respectively. 